Elevator

ABSTRACT

An elevator includes an elevator motor; a motor drive for the elevator motor having a frequency converter comprising a rectifier bridge, an inverter bridge and a DC link in between, which frequency converter is controlled via a controller, the rectifier bridge being connected to AC mains via three feed lines comprising chokes, and the rectifier bridge being realised via controllable semiconductor switches; a contactor being located between the feed lines and AC mains; a backup power supply at least for emergency drive operation; and an emergency control for performing an automatic emergency drive. The backup power supply is via a first switch connectable with only a first of said feed lines. A second and/or third of the feed lines is, via a second switch, connectable as power supply to a car door arrangement, the first switch, as well as the second switch, are controlled by the emergency control, and the emergency control is connected to a manual drive circuit having a manual drive switch for a manual rescue drive.

The present invention relates to an elevator comprising an elevatormotor, a motor drive for the elevator motor having a frequency convertercomprising a rectifier bridge, an inverter bridge and a DC link inbetween, which frequency converter is controlled via a controller, therectifier bridge being connected to mains via three feed linescomprising chokes, whereby the rectifier bridge is being realised viacontrollable semiconductor switches so that it is able to refeedelectricity into mains during generator mode of the elevator or elevatorgroup. Further, the elevator has a contactor being located between thefeed lines and mains as well as a backup power supply at least foremergency drive operation. To effect an emergency drive, the elevatorcomprises an emergency control for performing an automatic emergencydrive, which emergency control might be a separate component but ispreferably integrated with the controller. For feeding power to the DClink the backup power supply is via a first switch connectable with onlya first of said feed lines and the necessary Dc link voltage is providedvia a boost activity of at least one of the semiconductor switches ofthe rectifier bridge connected with the first feed line and the at leastone choke provided in the first feed line.

The controller regularly also controls the elevator brakes of theelevator to release them in normal operation as well as during anemergency drive. The backup power supply which is regularly realized viaa battery may also be formed by other power supplies as e.g.supercapacitors. This technology forms the background of the invention.Such kind of elevator is disclosed in the WO 2008/100259 A1.

It is object of the present invention to provide an elevator whichfacilitates and allows an automatic as well as manual emergency drive torelease trapped passengers.

The object is solved with an elevator according to claim 1. The objectis further solved with a method according to claim 16. Preferredembodiments of the invention are subject matter of the correlateddependent claims. Preferred embodiments of the invention are alsodescribed in the specification and drawings.

According to the invention, the second and/or third of said feed linesis via a second switch connectable to a power supply of an elevator cardoor, whereby the first switch connecting the backup power supply to thefirst feed line as well as the second switch connecting the power supplyof the elevator car door are controlled by the emergency control. Theemergency control again is connected to a manual drive arrangementhaving a manual drive switch for manual rescue drive.

This inventive solution enables the use of the rectifier bridge on onehand to act as a booster in connection with a choke in the first feedline to transform the DC voltage of the backup power supply, hereinafterbattery, to the required DC link voltage and the second and third feedline are simultaneously used to provide alternating current as powersupply for the elevator car door which power supply is connected via thesecond switch to the second and/or third feed line. Thus, the emergencycontrol which is usually integrated in the controller is able to releasethe elevator brakes and to start rotating the elevator motor to move theelevator car to the adjacent landing of the elevator. When the elevatorcar has arrived at the landing, the emergency control is via the secondand/or third feed line able to supply the necessary power for theelevator car door to open it so that the trapped passengers can bereleased. Of course, the emergency control feeds power for the elevatorcar door also during emergency drive, to provide closing torque to keepthe doors closed. The rectifier bridge which is a modulated rectifierbridge comprising of semiconductor switches controlled by the controlleris therefore able to simultaneously fulfil the task of increasing(boosting) the DC voltage for the DC link as well as to provide the ACvoltage for the elevator car door. The emergency control is therebyconnected to a manual drive arrangement having a manual drive switch forthe manual rescue drive which preferably enables the emergency controland/or the controller to be provided with power from the battery so thatit is able to release the elevator brakes and to rotate the elevatormotor preferably as long as the manual drive switch is pushed. There mayalso be more than one drive switch in the manual drive circuit, forexample separate mode a selection switch and then separate manual driveswitch.

Thus, the manual rescue drive can easily be performed. Of course, theelevator also comprises the automatic emergency drive function which isautomatically performed by the emergency control in case of a powerfailure of (public) AC mains. Only in case the automatic emergency drivefunction does not work, e.g. because the controller gets no supply powerand operating state of the elevator is therefore undefined, for example,elevator car position may be unknown, the emergency drive can beinitiated by the manual drive arrangement by pushing the manual driveswitch.

In a preferred embodiment of the invention, the backup power supply isconnected to the DC link via a DC/DC converter, preferably in flybacktopology. Via this measure, the capacitor of the DC link can be chargedup to a sufficient voltage level before connecting the first feed lineto the backup power supply to perform the boost action for the DC link.The advantage of the DC/DC converter is that the current provided by theDC/DC converter to the DC capacitor is limited so that the chargecurrent peak which is present at the start of the charge up of thecapacitor does not harm the DC/DC converter, the battery or the firstswitch. Furthermore, by the fact that now the DC link is charged up bythe DC/DC converter and the battery to a certain level, the current islimited when the semiconductors of the rectifier bridge connected to thefirst feed line begin the boosting of the battery voltage to the DC linkvoltage. If this action would start with an unloaded capacitor, the highinitial current might harm the corresponding semiconductors of therectifier bridge.

In a preferred embodiment, the DC/DC converter is bidirectional and isconfigured on one hand to generate a DC voltage for the DC link which ishigher than the battery voltage, and on the other hand the DC/DCconverter is configured to form a charging circuit for the battery fedfrom the DC link. Thus, the DC/DC converter has two functions, i.e. topre-charge the capacitor in case of mains power off so as to enable theabove-mentioned emergency drive action and on the other hand to chargethe battery during normal operation of the elevator. Via this measure,it is also ensured that the battery capacity is high enough in any caseof mains power off.

Preferably, the manual drive circuit is disposed in a remote controlunit outside of elevator shaft, so that the person performing the manualrescue drive does not need to enter the elevator shaft.

In a preferred embodiment of the invention a transformer is arrangedbetween the car door arrangement (door operator) and the second switch,so that the supply voltage can be easily adapted to the requirements ofthe door arrangement.

In an alternative embodiment, the DC/DC converter is one directionalsuch that is it configured only to charge the battery from the DC link.This means that the DC/DC controller only has one MOSFET transistor inthe DC link side of the transformer, and the other MOSFET transistor inthe battery side is not needed.

Preferably, the DC/DC converter comprises at least one PWM controller,preferably two PWM controllers, namely one on each side, which is/arecontrolled via the controller. The programs to control the PWMcontrollers are then preferably stored in the controller so that it isoptimized for battery charging during normal operation as well as forpre-charging the capacitor in the DC link during emergency drive.

In this connection it is to be mentioned that preferably a capacitor isprovided in the DC link which is the normal frequency converter topologyto minimize voltage ripple in the DC link.

In a preferred embodiment of the invention, the controller comprises anauxiliary power input being connectable to the backup power supply. TheDC link usually supplies power to the controller. Anyway, during periodsof non-use, e.g. during nights as well as in any case of mains poweroff, the voltage of the DC link might drop so that is not any longersufficient to form a power supply for the controller, at least toperform the emergency drive. In this case, this auxiliary power input isadvantageous as it can be connected to the backup power supply duringmains power off to ensure that all necessary operations in connectionwith an emergency drive, independent whether it is an automaticemergency drive or a manual emergency drive, can be performed.

Preferably, a second DC/DC converter is connected with the auxiliarypower input. This has the advantage that the second DC/DC converter canboost or reduce the incoming voltage to the voltage level which isadapted as supply voltage for the controller. In this connection it isadvantageous if the second DC/DC converter is a PWM-controlled whichenables a wide input voltage range. In this case it is preferable thatthe PWM of the second DC/DC converter has its own separated control asthe function of the controller is not ensured in case of mains power offbecause of missing supply voltage.

In a preferred embodiment of the invention, the DC/DC converter of thebattery is connected to the auxiliary power input, preferably to thesecond DC/DC converter, preferably via a diode. In this case, thecontroller may receive the energy from the DC/DC converter in a mainspower off situation when the DC/DC converter is starting to charge upthe capacitor in the DC link which provides a DC voltage which is higherthan that needed by the controller so that the voltage level can beadapted to the correct voltage for the controller by the second DC/DCconverter. By providing the diode between the DC/DC converter and thesecond DC/DC converter, it can be ensured that the voltage is onlyflowing in the direction from the DC/DC converter to the second DC/DCconverter and thus to the auxiliary power input of the controller. Sothe second DC/DC converter receives power from output of the DC/DCconverter when it has higher voltage than the battery, otherwise secondDC/DC converter receives power from the battery via the third switchwhereby the first and second diodes act as selector or the highest inputvoltage for the second DC/DC converter.

Preferably, an activation circuit is provided between the backup powersupply and the auxiliary power input, in which activation circuit athird switch is provided which is controlled via the emergency control(controller) as well as via the manual drive arrangement. Via thismeasure, power supply from the battery directly to the auxiliary powerinput—or to the second DC/DC converter connected to it—happens via thisactivation circuit. If the controller has still enough power, theemergency control closes the third switch which is preferably asemiconductor switch and thus it is ensured that the battery isconnected with the auxiliary power input of the controller, possibly viathe second DC/DC converter to ensure a correct voltage level. Thus, inany case of mains power off, a reliable function of the controller andthe emergency control is ensured via this activation circuit and thecontroller can keep awareness of current elevator status. On the otherhand, if the voltage level for the function of the emergency control(controller) is too low, the third switch cannot be closed via theemergency control itself as done during an automatic emergency drive. Inthis case, via pushing a manual drive switch in the manual drivearrangement, the third switch can be closed so that enough power isprovided for the emergency control (controller) to perform a manualemergency drive which also requires that via the emergency control(controller) the brakes are released. In some embodiments of the manualemergency drive, also the elevator motor is rotated and after arrival ata landing the car doors are opened. The emergency control (controller)is thus connected in any case to the battery via the activation circuit.The activation circuit is thereby closed either via the automaticemergency drive function of the emergency control itself or via themanual emergency drive function of the manual drive arrangement (pushinga manual drive switch in a manual drive circuit of the manual drivearrangement).

Preferably, the third switch is connected to the second DC/DC convertervia a diode, which ensures that power only flows one way to theauxiliary power input of the controller. As preferably also the firstDC/DC converter is connected to the auxiliary power input—or secondDC/DC converter—via a diode the power is fed to the auxiliary powerinput either from the DC/DC converter or from the activation circuit,i.e. which source provides the higher supply voltage level.

Preferably the second DC/DC converter is PWM-controlled enabling a wideinput voltage range.

Preferably, at least one capacitor is connected between the positive andnegative branch of the DC link. This capacitor smoothes the ripple inthe DC voltage of the DC link. Preferably this capacitor may be formedby a series connection of two capacitors in which case the connectionpoint of the two capacitors can be used as a neutral point of the DClink.

Preferably, the third switch in the activation circuit is controlled viaat least one semiconductor switch controlled by the emergency control aswell as by the manual drive arrangement. That means the emergencycontrol during its automatic emergency drive function controls the thirdswitch to close so that power is fed from the battery to the auxiliarypower input of the emergency control (controller).

Preferably, parallel to the semiconductor switch, a fourth switch in amanual drive circuit of a manual drive arrangement is connected, whichis preferably an opto-coupler. If the emergency control is not able toswitch on the third switch via the semiconductor switch, the switchingof the third switch can be realized by the fourth switch which isactivated via the manual drive circuit by pushing the manual driveswitch located therein. The embodiment of the fourth switch as anopto-coupler has the advantage that the manual drive circuit of themanual drive arrangement is galvanically isolated from the circuit ofthe elevator drive.

Preferably, the manual drive circuit in which the activating switch isconnected comprises a second backup power supply, preferably a secondbattery. The manual drive circuit is connected to the third switchpreferably via the opto-coupler. As the manual drive circuit isgalvanically isolated from the whole motor drive and controller, it ispreferable that the separated manual rescue switch has its own secondbackup power supply, preferably battery, which enables a reliable use ofthe manual drive arrangement in case of mains power off.

Preferably, at least one capacitor is connected between the positive andnegative branch of the DC link which enables a smooth DC link voltagepreferably when the DC link voltage is boosted via the connection of thebackup power supply to the first feed line in connection with its chokeand the corresponding semiconductor switches of the rectifier bridge.

It is further to be mentioned that the semiconductor switches of therectifier bridge connected to the first feed lines are operated duringboost operation preferably with a frequency of 100 Hz-10 kHz to providein connection with the choke located in the first feed line thesufficient DC voltage for the DC link. Hereby, the semiconductor switchof the lower half-bridge controls via its switching cycle the voltage,which is based on the inductance voltage peaks of the choke(s), whichvoltage peaks run via the anti-parallel diode of the upper semiconductorswitch to the positive branch of the DC link. Of course via this measurea voltage is boosted which is much higher than the feed voltage of thebackup power supply.

Preferably, the semiconductor switches of the rectifier bridge areprovided with antiparallel diodes, so that easier voltage boostingfunction in the above sense is enabled.

The invention also refers to a method for performing a rescue operationin an elevator according to the type which is described above. Thismethod works as follows: In case of mains power off, the contactors areopened so that the feed lines are no longer connected with AC mains.Then, the backup power supply is initiated to feed direct current to theDC link via the DC/DC converter which boosts the DC voltage to a levelwhich is adapted for the DC link (regularly several hundred volts) fromthe battery voltage level (regularly 20 to 63 V). This pre-charges thecapacitor in the DC link.

The emergency control (controller) then energizes an activation circuitvia the emergency control or via a manual drive circuit, whichactivation circuit connects the backup power supply to an auxiliarypower input of the emergency control to selectively perform an automaticor manual emergency drive. The backup power supply is connected to thefirst feed line and the lower semiconductor of the rectifier bridgeconnected to the first feed line is controlled to switch, e.g. with afrequency between 100 Hz and 100 kHz which is optimal for voltageboosting. In the automatic rescue drive, the emergency control energizesthe elevator brakes to release by controlling power supply from the DClink to the brakes and begins rotating the elevator motor via control ofthe inverter bridge, whereas in the manual rescue drive, the emergencycontrol at least energizes the elevator brakes to release by controllingpower supply from the DC link to the brakes, in which case the car maye.g. move by its gravitational force.

Via the semiconductor switches connected to the second and/or third feedline an AC voltage is created in the second and/or third feed line whichis/are connected as power supply to the door arrangement of the elevatorcar.

After the elevator car has reached a landing zone the car doors areopened to release the passengers with the supply voltage fed via thesecond and/or third feed line.

Via the semiconductor switches of the rectifier bridge connected to thesecond and third feed line, an AC voltage is created in these feedlines, and the second and/or third feed line is connected via a secondswitch to the door arrangement, i.e. door drive and door controller ofthe elevator car as a power supply. If only one of the second or thirdfeed line is connected as a power supply to the car arrangement theother pole for the power supply has to be created by a neutral voltagelevel of the DC link. This neutral point could be created for example byusing the connection point between two capacitors which are connected inseries between the two branches of the DC link. Thus either the powersupply is between the second or third feed line on one hand and theneutral point on the other hand or between the second and third feedline. After the elevator car has reached a landing zone, the car doorsare then opened via the connection of the second and/or third feed lineto the door drive of the elevator car. Thus, an automatic as well asmanual emergency drive for releasing trapped passengers is possible inan economical way.

Preferably, a transformer is arranged between the car door arrangementand the second switch such that the AC voltage created in the second andthird feed lines is supplied to the transformer and transformed to anadapted voltage for the door arrangement.

Preferably, a manual drive switch in a manual drive arrangement ispressed to energize the activation circuit which leads to a connectionof the backup power supply with the (auxiliary) power input of thecontroller/emergency control. This enables the activation of thecontroller even if it is in an unpowered state via manual operation ofthe manual drive arrangement.

Preferably, the DC/DC converter which is used to pre-charge thecapacitor in the DC link before connecting the backup power supply tothe first feed line is used in a normal elevator operation as a chargingcircuit for the backup power supply. Thus, the different functions canbe realized with a minimum of hardware components.

It shall be clear that the controller may be a separate or integratedpart of the elevator control, and it may comprise or being connectedwith the control of the elevator brakes to release the elevator brakesduring an emergency drive. Hereinafter, the control of the elevatorbrakes is described to be integrated with the controller, but it isclear that it may be a separate control component connected to theelevator control and/or controller. The controller is usually a digitalsignal processor which is connected by control lines with thesemiconductors of the rectifier bridge as well as of the inverter bridgeand it has inputs for obtaining status data of the elevator motor asvelocity and electric values of the inverter bridge and of the elevatormotor.

Above, the power supply to the emergency control (controller) in case ofmains power off has been realized via its auxiliary power input. Ofcourse, the auxiliary input is preferable but not really necessary toperform the above functions. In this case the power is fed from theDC/CD converter or activation circuit to the (normal) power input of theemergency control (controller).

The semiconductor switches of the rectifier bridge and/or inverterbridge may preferably be IGBTs or MOSFETs or SiC MOSFETs.

It shall be clear for the skilled person that the above-mentionedembodiments may be combined with each other arbitrarily.

Following terms are used as synonyms: backup power supply—battery;rectifier bridge—modulated rectifier bridge; DC/DC converter—first DC/DCconverter; capacitor—smoothing capacitor; elevator brake—motor brake;landing zone indicator—door zone indicator; fourth switch—opto coupler;

The invention is hereinafter described via a preferred embodiment inconnection with the drawings.

FIG. 1 shows an electric diagram of the motor and brake drive section ofan elevator including automatic and manual emergency drive components,and

FIG. 2 shows an electric diagram similar to FIG. 1 with a simplifiedcharging arrangement for the backup power supply.

FIG. 1 shows an elevator 10 comprising an elevator motor 12 which iscontrolled by an elevator drive 14 which is embodied as a frequencyconverter comprising a modulated rectifier bridge 16 consisting ofsemiconductor switches with antiparallel diodes, an inverter bridge 18and a DC link 20 in between. The DC link 20 comprises a smoothingcapacitor 22. The elevator motor 12 comprises preferably a tractionsheave 24 over which a hoisting rope 26 is running carrying an elevatorcar 28 and optionally a counterweight 30. Alternatively, the hoistingrope 26 may be connected with the underside of the car to build a closedloop (with or without counterweight 30). Further, the elevator motor 12comprises two parallel elevator brakes 32 a, 32 b. Finally, a controller34 is provided which additionally forms an emergency control 35 of theelevator drive 14. The controller 34 controls the semiconductor switches17 of the rectifier bridge 16, the semiconductor switches of theinverter 18, the elevator brakes 32 a, 32 b and it is connected with alanding zone indicator 36 showing whether or not the elevator car hasarrived a landing zone of the elevator 10. Preferably the controllergets input of the electrical values of the inverter bridge and elevatormotor and eventually a tachometer signal of an encoder at the motorshaft or traction sheave.

The rectifier bridge 16 is connected via three feed lines 38 a-c to amain contactor 40. The three feed lines 38 a-c are connected via themain contactor 40 with AC mains 42, i.e. with normally a three-phase ACpublic network. In each feed line 38 a-38 c, two chokes 44 a, 44 b arelocated. Between the feed lines 38 a-38 c, a capacitor bridge 46 isconnected which in connection with the chokes 44 a and 44 b act as an ACline filter. The elevator drive 14 comprises a backup power supply 48preferably in form of a battery which is connected to a DC/DC converter50, preferably in a flyback topology. The DC/DC converter 50 compriseson both sides a PWM controller which is controlled by the controller 34.The battery 48 is connected via a first switch 52 to the first feed line38 a. The first switch 52 also disconnects the capacitor bridge 46 fromthe first feed line 38 a simultaneously with connection to the battery48. The second and third feed line are connected with second switches 54a, 54 b with door arrangement 56 comprising a door controller as well asa door drive and the car door.

The controller 34 has preferably an auxiliary power input 58 connectedpreferably to a second DC/DC converter 60. The second DC/DC converter 60acts as a kind of voltage regulator for the auxiliary power input 58 ofthe controller 34.

While the first branch of the DC/DC converter 50 is connected with thebattery 48, the second branch is connected to the DC link 20.Furthermore, additionally the second branch of the DC/DC converter 50 isconnected via a first diode 62 to the second DC/DC converter 60 at theauxiliary power input 58 of the controller 34. The battery 48 is via anactivation circuit 64 directly connected to the second DC/DC converter60, and thus to the auxiliary power input 58 of the controller 34. Theactivation circuit 64 comprises a third switch 66 and a second diode 68.So the second DC/DC converter 60 receives power from output of the DC/DC50 converter when it has higher voltage than the battery 48, otherwisesecond DC/DC converter 60 receives power from the battery 48 via thethird switch 66 whereby the first and second diodes 62 and 68 act asselector or the highest input voltage for the second DC/DC converter 60.

In this activation circuit 64 the third switch 66 is preferably asemiconductor switch which is activated via a boost transistor 72connected to the gate of the third switch 66. The boost transistor 72 iscontrolled either via a transistor 70 (or other semiconductor switch)which is controlled via the controller 34 in case of an automaticemergency drive. Or the boost transistor 72 is controlled a fourthswitch 74 preferably in form of an opto-coupler. This fourth switch 74is connected in parallel to the transistor 70 and is comprised in amanual drive circuit 78 of a manual drive arrangement 76. The manualdrive circuit 78 comprises a second backup power supply (battery) 80 anda manual drive switch 82. The manual drive circuit 78 is connected tothe other components of the elevator drive 14 via the opto-coupler 74.This means that the third switch 66 in the activation circuit 64 iscontrolled either via the transistor 70 or via the opto-coupler 74 ofthe manual drive circuit 78, which two alternative ways correspond to anautomatic or manual emergency drive of the elevator car, particularly incase of AC mains power off. The function of the elevator 10 in anemergency case is carried out hereinafter: In case of a power off of themains 42, the main contactor 40 is opened. Now, there are two cases.

The first case is that the voltage level in the DC link 20 issufficiently high enough for the controller 34 to operate. In this case,the transistor 70 controlled by the controller 34, i.e. the emergencycontrol 35 thereof, is activated which closes the third switch 66 in theactivation circuit 64 so that the battery 48 is via the second DC/DCconverter 60 connected to the auxiliary power input 58 of the controller34. This power supply via the activation circuit 64 to the auxiliarypower input 58 enables the controller 34 to operate properly. Now thecontroller 34 controls the two PWM controllers of the DC/DC converter 50to charge up the smoothing capacitor 22 in the DC link 20. After thevoltage in the DC link 20 has reached a sufficient level, the firstswitch 52 is closed by the controller 34 so that the battery 48 isconnected to the first feed line 38 a. Simultaneously, the capacitorbridge 46 is separated from the first feed line 38 a. Now, a DC voltageis connected to the first feed line 38 a and the lower semiconductor 17f of the rectifier bridge 16 is controlled to open and close in afrequency of about 100 Hz to 10 kHz. This leads to corresponding voltagepeaks of the chokes 44 a and 44 b in the first feed line 38 a whichvoltage flows via the antiparallel diode of the upper semiconductor 17 cto the DC link 20 and charges it to a desired voltage level. Via thefact that the smoothing capacitor 22 in the DC link has been pre-chargedby the DC/DC converter 50, the current flowing through the antiparalleldiode 17 c is not too high for it to be harmed. Now, also the DC link 20has a sufficient voltage level so that the second switches 54 a, 54 bcan be closed to energize the door arrangement 56 to ensure that the cardoors are closed during emergency drive. The controller 34 now controlsthe elevator brakes 32 a and 32 b to release and controls thesemiconductors in the inverter bridge 18 to rotate the elevator motor12. When the elevator car 28 has reached the level of a door zone, thisis signalized to the controller 34 via landing zone indicator 36. Thenthe controller 34 stops rotating the elevator motor 12 and de-energizesthe elevator brakes 32 a, 32 b enabling them to grip and keep thetraction sheave 24 stopped. Now, the controller 34 initiates the doorcontrollers and door drives of the door arrangement 56 to open the cardoor which is possible via the power supply via the second and thirdfeed lines 38 b and 38 c which are connected to the door drive and doorcontroller via second switch 54 a, 54 b. As normally the car doorsconnectors are coupled to the corresponding landing doors both areopened and the trapped passengers can be released.

If in a second situation the voltage level in the DC link at thebeginning of the emergency drive is not sufficiently high for thecontroller 34 to work, the controller 34 is not able to activate thetransistor 70 to close the third switch 66 in the activation circuit 64.In this case, a maintenance person or an operator has to push a manualdrive switch 82 in the manual drive circuit 78 which closes the fourthswitch 74 parallel to the transistor 70 and thus closes via boosttransistor 72 the third switch 66 connecting the battery 48 to thesecond DC/DC converter 60 at the auxiliary power input 58 of thecontroller 34 via the second diode 68. Now, the controller 34 is able towork and to start the necessary steps for performing the manualemergency drive as mentioned above with starting pre-charging thecapacitor 22 in the DC link 20 via the DC/DC converter 50. Usually themanual drive switch has to be kept pushed until the car has arrived at alanding and the doors are opened so that the trapped persons may bereleased.

The automatic emergency drive maybe started automatically or controlledvia a remote maintenance centre, which is connected to the controller 34(and/or the elevator control) via a public communication network.

An alternative embodiment shown in FIG. 2 is almost identical to FIG. 1with the difference that the DC/DC converter 51 is only one directionalsuch that is it configured only to charge the battery 48 from the DClink, but in contrast to FIG. 1 it is not able to feed boosted DCvoltage to the DC link 20. In this case the DC/DC controller 51 only hasone PWM controlled MOSFET transistor in the DC link side of thetransformer, and the other MOSFET transistor in the battery side is notneeded.

In this alternative embodiment, the initial charging of DC link takesplace via a pre-charge line 83 in which a current limiting resistor anda third diode is connected. This pre-charge line is connected betweenthe output of the third switch 64 and the positive branch DC+ of the DClink 20. This embodiment has the advantage of lower cost. Of course inthis case the capacitor 22 can only be charged to the voltage level ofthe battery 48.

The capacitor 22 in the DC link 20 can also be formed by a seriesconnection of two capacitors in which case the connection point of thetwo capacitors is used as a neutral point of the DC link, e.g. forconnecting the door arrangement 56 between only one of the second orthird feed line 38 b, 38 c and this neutral point.

The above elevator therefore allows automatic as well as manualemergency drive operation with a minimum of hardware components and witha high level of security and reliability.

The invention is not restricted to the disclosed embodiments but may bevaried within the scope of the claims as attached.

LIST OF REFERENCE NUMBERS

-   10 elevator-   12 elevator motor-   14 elevator drive-   16 rectifier bridge-   18 inverter bridge-   20 DC link (DC+, DC−)-   22 smoothing capacitor-   24 traction sheave-   26 hoisting rope—a set of hoisting ropes-   28 elevator car-   30 counterweight-   32 a,b elevator brakes—motor brakes-   34 controller (including emergency control, e.g. being part of the    elevator control)-   35 emergency control-   36 landing zone indicator—door zone indicator-   38 a,b,c three feed lines to the rectifier bridge-   40 main contactor-   42 AC mains (public AC network)-   44 a first chokes in the feed lines-   44 b second chokes in the feed lines-   46 capacitor bridge-   48 backup power supply—battery-   50 (first) DC/DC converter-   52 first switch (relay)-   54 a,b second switch-   56 door arrangement (door drive with door controller and car door)-   58 auxiliary power input of the controller-   60 second DC/DC converter at auxiliary power input-   62 first diode between DC/DC converter and second DC/DC converter-   64 activation circuit-   66 third switch-   68 second diode-   70 transistor controlled by the controller-   72 boost transistor for third switch-   74 fourth switch—opto coupler-   76 manual drive arrangement-   78 manual drive circuit-   80 second backup power supply—second battery in the manual drive    circuit-   82 manual drive switch-   83 pre-charge line-   84 resistor-   86 third diode

The invention claimed is:
 1. An elevator comprising: an elevator motor;a motor drive for the elevator motor having a frequency convertercomprising a rectifier bridge, an inverter bridge and a DC link inbetween, the frequency converter being controlled via a controller, therectifier bridge being connected to AC mains via three feed linescomprising chokes, and the rectifier bridge being realised viacontrollable semiconductor switches; a contactor located between thefeed lines and the AC mains; a backup power supply, at least foremergency drive operation; and an emergency control for performing anautomatic emergency drive, wherein the backup power supply is, via afirst switch, connectable with only a first of said feed lines, whereina second and/or third of said feed lines is, via a second switch,connectable as power supply to a car door arrangement, while the secondand third feed lines are separated from the AC mains with the contactor,wherein the first switch, as well as the second switch, are controlledby the emergency control, wherein the emergency control is connected toa manual drive circuit having a manual drive switch for a manual rescuedrive, wherein the controller comprises an auxiliary power input beingconnectable to the backup power supply, and wherein an activationcircuit is provided between the backup power supply and the auxiliarypower input, in which activation circuit a third switch is providedwhich is controlled via the emergency control and via the manual drivecircuit.
 2. The elevator according to claim 1, wherein the emergencycontrol is integrated with the controller.
 3. The elevator according toclaim 1, wherein the backup power supply is connected to the DC link viaa DC/DC converter.
 4. The elevator according to claim 3, wherein theDC/DC converter is bidirectional and is configured to generate a DCvoltage for the DC link which is higher than the backup power supplyvoltage, and which DC/DC converter is further configured to be acharging circuit for the backup power supply fed from the DC link. 5.The elevator according to claim 3, wherein the DC/DC converter is onedirectional and a pre-charge line is connected between the backup powersupply and the positive busbar (DC+) of the DC link.
 6. The elevatoraccording to claim 3, wherein the DC/DC converter comprises at least onePWM controller which is/are controlled via the controller.
 7. Theelevator according to claim 3, wherein a second DC/DC converter islocated in the auxiliary power input.
 8. The elevator according to claim3, wherein a second DC/DC converter is located in the auxiliary powerinput, and wherein the DC/DC converter is connected to the auxiliarypower input, to the second DC/DC converter, via a first diode.
 9. Theelevator according to claim 8, wherein the third switch is connected tothe second DC/DC converter via a second diode.
 10. The elevatoraccording to claim 1, wherein the third switch is controlled via atleast one transistor controlled by the emergency control.
 11. Theelevator according to claim 10, wherein parallel to the transistor afourth switch of a manual drive circuit is connected.
 12. The elevatoraccording to claim 11, wherein the manual drive circuit comprises asecond backup power supply and a manual drive switch, which manual drivecircuit controls the third switch via an opto-coupler.
 13. The elevatoraccording to claim 1, wherein the backup power supply is or comprises abattery.
 14. A method for performing a rescue operation in an elevator,the elevator comprising: an elevator motor; a motor drive for theelevator motor having a frequency converter comprising a rectifierbridge, an inverter bridge and a DC link in between, the frequencyconverter being controlled via a controller, the rectifier bridge beingconnected to AC mains via three feed lines comprising chokes, and therectifier bridge being realised via controllable semiconductor switches;a contactor located between the feed lines and the AC mains; a backuppower supply, at least for emergency drive operation; and an emergencycontrol for performing an automatic emergency drive, wherein the backuppower supply is, via a first switch, connectable with only a first ofsaid feed lines, wherein a second and/or third of said feed lines is,via a second switch, connectable as power supply to a car doorarrangement, while the second and third feed lines are separated fromthe AC mains with the contactor, wherein the first switch, as well asthe second switch, are controlled by the emergency control, and whereinthe emergency control is connected to a manual drive circuit having amanual drive switch for a manual rescue drive the method comprising thefollowing steps: in case of mains power off, the contactor is opened andthe backup power supply is initiated to feed direct current to the DClink via a DC/DC converter; an activation circuit is energized via theemergency control or via a manual drive circuit, the activation circuitconnecting the backup power supply with an auxiliary power input of theemergency control to selectively perform an automatic or manualemergency drive; the backup power supply is connected to the first feedline and the lower semiconductor of the rectifier bridge connected tothe first feed line is controlled to switch with a frequency between 100Hz and 100 kHz; in the automatic rescue drive, the emergency controlenergizes the elevator brakes to release by controlling power supplyfrom the DC link to the brakes and begins rotating the elevator motorvia control of the inverter bridge; and in the manual rescue drive, theemergency control at least energizes the elevator brakes to release bycontrolling power supply from the DC link to the brakes; via thesemiconductor switches connected to the second and third feed line an ACvoltage is created in the second and/or third feed line which is/areconnected as power supply to the door arrangement of the elevator car;and after the elevator car has reached a landing zone the car doors areopened to release the passengers with the supply voltage fed via thesecond and/or third feed line.
 15. The method according to claim 14,wherein in the manual rescue drive the emergency control energizes theelevator brakes to release by controlling power supply from the DC linkto the brakes and begins rotating the elevator motor via control of theinverter bridge.
 16. The method according to claim 15, wherein, if theemergency control has closed down so that the activation circuit is notenergized by the emergency drive, a manual drive switch in a manualdrive circuit is pressed which leads to closing of the activationcircuit.
 17. A method for operating an elevator and designed to use themethod for performing a rescue operation according to claim 16, whereinthe DC/DC converter is used in normal elevator operation to charge thebackup power supply.
 18. The elevator according to claim 3, wherein theDC/DC converter is one directional and a pre-charge line is connectedbetween the backup power supply and the positive busbar (DC+) of the DClink via the third switch of an activation circuit.